1. Field of Invention
This invention relates to a hitless migration method and apparatus for upgrading an ATM network.
2. Description of Related Art
Currently, telecommunications carriers and service providers widely use Asynchronous Transfer Mode (ATM) technology in their networks. Due to the. ATM widely installed base and the continued evolution of this technology, ATM networks often need to be upgraded as new features or in some cases standard-based implementations become available. However, in many cases these upgrades can result in service disruptions, e.g., service hits in the network. For example, a customer can experience downtime and service outages, e.g., for minutes or even hours, during a typical ATM network upgrade. The typical practice is to interrupt/takedown service during an upgrade. For instance, in private line service, customer downtime can be a big issue, costing a customer and a service provider a large sum of money.
One reason for migrating to a new network can be a service-affecting upgrade of an existing switch network. Another reason can be replacing an existing switch with a new switch to obtain better performance or price. For example, a current vendor might not support the desired features or interfaces, or the current switch can not be scaled up to the newly required performance and capacity.
Due to the explosive growth in the demand in data services, the number of customers and the amount of bandwidth that customers require, there will inevitably be a need to scale up current switches to keep up with new performance and capacity requirements. Service providers are faced with the need to do network maintenance and upgrades without adversely impacting the customers.
This invention provides a system and method for upgrading an ATM network to a new release of a vendor""s ATM platform or for converting an ATM network to a different vendor""s ATM platform without experiencing any noticeable service disruptions. The system and method of the present invention consists of taking an existing redundant ATM network and reorganizing that network by splitting the redundant links- for example, fiber links- within the existing redundant ATM network among two parallel networks without adding any additional links. For illustrative purposes, these two parallel networks are called Network A and Network B.
Initially, an existing network is ideally setup whereby there are at least two paths for each circuit, e.g., a redundancy setup. The redundant setup allows a system administrator to remove redundant links from Network A to use in Network B. The networks are basically seen as links connecting ATM switches with each other. Upon reorganizing the existing old network into two parallel networks, i.e., Network A and Network B, Network A and Network B will resemble the old existing network without the linkage redundancy, however, Network A may now include an upgrade.
Instead of one network, we will now have two established networks comprising similar links and circuits. The links within each of the two newly established separate networks are non-redundant. One network can be used for upgrading purposes and the other network can be used for continuing uninterrupted service to the customers. Connectivity between the two nodes will be established, for example, by using a SONET ring infrastructure to carry signals between ATM nodes in both networks.
Network A can represent a network in which circuits will be upgraded and Network B can represent a network which is used for continuing service to the customers during the upgrade. In network A, a service-affecting upgrade or a replacement of an existing switch may be required. Network B will be using techniques from the old network architecture. Once all necessary hardware replacements are made in Network A and after a successful hitless upgrade, i.e., a performance objective of no more than 3 short failure events per month, of Network A, the physical links used in Network B can be moved to the newly upgraded ATM Network A.
In other words, circuits are systematically moved from Network B to Network A by preferably using a Bridge and Roll technique. After circuits have been moved and tested, the customer traffic from Network B is migrated to Network A, preferably without experiencing any noticeable customer disruptions. Finally, an upgraded redundant-based ATM network can be established by transferring the links in Network B to Network A.
These and other aspects of the invention will be apparent or obvious from the following description.